Recuperating passive and active suspension

ABSTRACT

An automobile includes an active suspension system and a leveling system. The leveling system receives high pressure fluid from the active suspension system in order to change static vehicle height and compensate for static load changes.

FIELD

The present disclosure is directed to an active suspension system. Moreparticularly, the present disclosure is directed to an active suspensionsystem that incorporates a leveling system in conjunction with theactive suspension system.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Suspension systems are provided to filter or isolate the vehicle's body(sprung portion) from the vehicle's wheels and axles (unsprung portion)when the vehicle travels over vertical road surface irregularities aswell as to control body and wheel motion. In addition, suspensionsystems are also used to maintain an average vehicle attitude to promoteimproved stability of the vehicle during maneuvering. The typicalpassive suspension system includes a spring and a damping device inparallel with the spring which are located between the sprung portionand the unsprung portion of the vehicle.

Hydraulic actuators, such as shock absorbers and/or struts, are used inconjunction with conventional passive suspension systems to absorbunwanted vibration which occurs during driving. To absorb this unwantedvibration, hydraulic actuators include a piston located within apressure cylinder of the hydraulic actuator. The piston is connected toone of the unsprung portion or suspension and the sprung portion or bodyof the vehicle through a piston rod. The pressure tube is connected tothe other of the unsprung portion and sprung portion of the vehicle.Because the piston is able to restrict the flow of damping fluid withinthe working chamber of the hydraulic actuator when the piston isdisplaced within the pressure cylinder, the hydraulic actuator is ableto produce a damping force which counteracts the vibration of thesuspension. The greater the degree to which the damping fluid within theworking chamber is restricted by the piston, the greater the dampingforces which are generated by the hydraulic actuator.

In recent years, substantial interest has grown in automotive vehiclesuspension systems which can offer improved comfort and road handlingover the conventional passive suspension systems. In general, suchimprovements are achieved by utilization of an “intelligent” suspensionsystem capable of electronically controlling the suspension forcesgenerated by hydraulic actuators.

Different levels in achieving the ideal “intelligent” suspension systemcalled a semi-active or a fully active suspension system are possible.Some systems control and generate damping forces based upon the dynamicforces acting against the movement of the piston. Other systems controland generate damping forces based on the static or slowly changingdynamic forces, acting on the piston independent of the velocity of thepiston in the pressure tube. Other, more elaborate systems, can generatevariable damping forces during rebound and compression movements of thehydraulic actuator regardless of the position and movement of the pistonin the pressure tube.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present disclosure provides the art with a leveling system which isin communication with an active suspension system. The fluid pressureused to control the active suspension system is provided to the levelingsystem to change the height of the vehicle.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a diagrammatic illustration of a vehicle incorporating theleveling system and the active suspension system in accordance with thepresent disclosure;

FIG. 2 is a schematic view of one of the corner assemblies including thehydraulic actuator illustrated in FIG. 1 illustrating the components ofthe hydraulic actuator;

FIG. 3 is a schematic view of fluid connection between the hydraulicactuator for the active suspension system and the leveling system; and

FIG. 4 is a schematic view of a corner assembly including a hydraulicactuator in accordance with another embodiment of the presentdisclosure.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application or uses. There isshown in FIG. 1 a vehicle incorporating a suspension system having asuspension system in accordance with the present disclosure and which isdesignated generally by the reference numeral 10. Vehicle 10 comprises arear suspension 12, a front suspension 14 and a body 16. Rear suspension12 has a transversely extending rear axle assembly (not shown) adaptedto operatively support the vehicle's rear wheels 18. The rear axleassembly is operatively connected to body 16 by means of a pair ofcorner assemblies 20 which include a pair of shock absorbers 22 and apair of helical coil springs 24. Similarly front suspension 14 includesa transversely extending front axle assembly (not shown) to operativelysupport the vehicle's front wheels 26. The front axle assembly isoperatively connected to body 16 by means of a second pair of cornerassemblies 28 which include a pair of shock absorbers 30 and by a pairof shaped helical coil springs 32. Shock absorbers 22 and 30 serve todampen the relative motion of the unsprung portion (i.e. front and rearsuspensions 12 and 14, respectively) and the sprung portion (i.e. body16) of vehicle 10. While vehicle 10 has been depicted as a passenger carhaving front and rear axle assemblies, shock absorbers 22 and 30 may beused with other types of vehicles and/or in other types of applicationssuch as vehicles incorporating independent front and/or independent rearsuspension systems. Further, the term “shock absorber” as used herein ismeant to be dampers in general and thus will include struts. Also, whilefront suspension 14 is illustrated having a pair of struts or shockabsorbers 30, it is within the scope of the present invention to haverear suspension 12 incorporate a pair of struts or shock absorbers 30 ifdesired. As illustrated in FIG. 1, shock absorber 22 is separate fromspring 24. In this configuration, the adjustable spring seat is disposedbetween the sprung and unsprung portions of the vehicle. Also, shockabsorber 22 and spring 24 can be replaced with corner assemblies 28.

Referring now to FIG. 2, the front corner assembly 28 for vehicle 10 isillustrated in greater detail. Body 16 defines a shock tower 34comprising sheet metal of vehicle 10 within which is mounted a strutassembly 36 which comprises a telescoping device in the form of shockabsorber 30, coil spring 32, a top mount assembly 38 and a knuckle 40which is part of a wheel assembly. Strut assembly 36 including shockabsorber 30, coil spring 32 and top mount assembly 38 are attached tovehicle 10 using shock tower 34. Top mount assembly 38, a part of thesprung portion of the vehicle, comprises a top mount 42, a bearingassembly 44 and an upper spring seat 46. Top mount 42 comprises anintegral molded body and a rigid body member, typically made of stampedsteel. Top mount assembly 38 is mounted to shock tower 34 by bolts 48.Bearing assembly 44 is friction fit within the molded body of top mount42 to be seated in top mount 42 so that one side of bearing assembly 44is fixed relative to top mount 42 and shock tower 34. The second side ofbearing assembly 44 freely rotates with respect to the first side ofbearing assembly 44, top mount 42 and shock tower 34.

The free rotating side of bearing assembly 44 carries upper spring seat46 that is clearance fit to the outer diameter of bearing assembly 44.An elastomeric jounce bumper 50 is disposed between upper spring seat 46and shock absorber 30. Elastomeric jounce bumper 50 comprises anelastomeric material which is protected by a plastic dirt shield 52.

A hydraulic adjustable lower spring seat assembly 56, which is part ofthe unsprung portion of the vehicle, is attached to shock absorber 30and coil spring 32. Coil spring 32 is disposed between upper spring seat46 and lower spring seat assembly 56 to isolate body 16 from frontsuspension 14. While shock absorber 30 is illustrated in FIG. 2, it isto be understood that shock absorber 22 may also include the featuresdescribed herein for shock absorber 30.

Prior to the assembly of strut assembly 36 into vehicle 10, thepre-assembly of strut assembly 36 is performed. Elastomeric jouncebumper 50 and plastic dirt shield 52 are assembled to shock absorber 30.Coil spring 32 is assembled over shock absorber 30 and positioned withinlower spring seat assembly 56. Upper spring seat 46 is assembled ontoshock absorber 30 and correctly positioned with respect to coil spring32. Bearing assembly 44 is positioned on top of upper spring seat 46 andtop mount 42 is positioned on top of bearing assembly 44. This entireassembly is positioned within an assembly machine which compresses coilspring 32 such that the end of shock absorber 30 extends through a borelocated within top mount assembly 38. A retaining nut 58 is threadinglyreceived on the end of shock absorber 30 to secure the assembly of strutassembly 36.

Top mount 42 is designed as an identical component for the right andleft hand sides of the vehicle but it has a different orientation withrespect to shock absorber 30 and its associated bracketry when it isplaced on the right or left side of the vehicle.

Hydraulic adjustable spring seat assembly 56 includes an inner housingassembly 60 attached to shock absorber 30 and an outer housing assembly62 that is attached to both shock absorber 30 and coil spring 32. Innerhousing assembly 60 and outer housing assembly 62 define a fluid chamber64. When fluid is added to fluid chamber 64, outer housing assembly 62will move upward along shock absorber 30, as illustrated in FIG. 2. Thismovement will raise vehicle body 16 with respect to front suspension 14.When fluid is removed from fluid chamber 64, outer housing assembly 62will move downward along shock absorber 30, as illustrated in FIG. 2.This movement will lower vehicle body 16 with respect to frontsuspension 14. Fluid chamber 64 is in fluid communication with shockabsorber 30 as described below.

Shock absorber 30 is a mono-tube designed shock absorber comprising apressure tube 70, a piston assembly 72 and a piston rod 74.

Pressure tube 70 defines a fluid chamber 76. Piston assembly 72 isslidably disposed within pressure tube 70 and divides fluid chamber 76into an upper working chamber 78 and a lower working chamber 80. A sealis disposed between piston assembly 72 and pressure tube 70 to permitsliding movement of piston assembly 72 with respect to pressure tube 70without generating undue frictional forces as well as sealing upperworking chamber 78 from lower working chamber 80. Piston rod 74 isattached to piston assembly 72 and extends through upper working chamber78 and through an upper end cap 82 which closes the upper end ofpressure tube 70. A sealing system seals the interface between upper endcap 82, pressure tube 70 and piston rod 74. The end of piston rod 74opposite to piston assembly 72 is adapted to be secured to the one ofsprung and unsprung mass of vehicle 10. Valving within piston assembly72 controls the movement of fluid between upper working chamber 78 andlower working chamber 80 during movement of piston assembly 72 withinpressure tube 70. Because piston rod 74 extends only through upperworking chamber 78 and not lower working chamber 80, movement of pistonassembly 72 with respect to pressure tube 70 causes a difference in theamount of fluid displaced in upper working chamber 78 and the amount offluid displaced in lower working chamber 80. The difference in theamount of fluid displaced is known as the “rod volume” and it isaccommodated for by the use of a floating piston 84 as is well known inthe art. An end cap 86 seals the end of pressure tube 70.

Referring to FIG. 3, a hydraulic actuator assembly 90 comprises shockabsorber 30, a low pressure accumulator subsystem 92, one or morepressure divider subsystems 94, and a flow divider subsystem 100.

Low pressure accumulator subsystem 92 comprises a low pressureaccumulator 110, a first check valve 112 and a second check valve 114.First check valve 112 allows fluid flow from low pressure accumulator110 to upper working chamber 78 but prohibits fluid flow from upperworking chamber 78 to low pressure accumulator 110. Second check valve114 allows fluid flow from low pressure accumulator 110 to lower workingchamber 80 but prohibits fluid flow from lower working chamber 80 to lowpressure accumulator 110. Low pressure accumulator 110 is connected to apair of blow-off valves 116, the one or more pressure divider subsystems94 and flow divider subsystem 100.

The two pressure divider subsystems 94 illustrated in FIG. 3 include arebound pressure divider subsystem 94 (the upper pressure dividersubsystem) and a compression pressure divider subsystem 94 (the lowerpressure divider subsystem). Each pressure divider subsystem 94comprises a controlled restriction 120. In rebound pressure dividersubsystem 94, controlled restriction 120 is located between upperworking chamber 78 and flow divider subsystem 100 and between upperworking chamber 78 and low pressure accumulator 110. In the compressionpressure divider subsystem 94, controlled restriction 120 is locatedbetween lower working chamber 80 and flow divider subsystem 100 andbetween lower working chamber 80 and low pressure accumulator 110.

Pressure divider subsystem 94 creates a requested pressure in upperworking chamber 78 and/or lower working chamber 80.

Flow divider subsystem 100 comprises a pump 130, a hydraulic switchvalve 132 and a pair of check valves 134. Flow divider subsystem 100controls the hydraulic energy from pump 130. Pump 130 receives fluidfrom low pressure accumulator 110. Fluid from pump 130 is directed tohydraulic switch valve 132. Hydraulic switch valve 132 can guide fluidflow to upper working chamber 78 and/or lower working chamber 80depending on where it is needed. Hydraulic switch valve 132 can alsodivide the flow between upper working chamber 78 and lower workingchamber 80 in a continuously controlled manner. While hydraulic switchvalve 132 is illustrated using a symbol of a switch valve, this is notintended to limit the disclosure. Check valves 134 prohibit fluid flowfrom upper working chamber 78 and lower working chamber 80 to flowdivided subsystem 100.

As illustrated in FIG. 3, fluid chamber 64 of hydraulic adjustablespring seat assembly 56 is in fluid communication with hydraulicactuator assembly 90. This connection allows for the changing of thestatic vehicle height and the compensation for static load changes byadjusting the height of body 16 with respect to front suspension 14based upon the fluid pressures within hydraulic actuator assembly 90.

When an increased static (or quasi-static) push-out force must becreated in shock absorber 30, hydraulic actuator assembly 90 willdeliver this force by increasing the pressure in lower working chamber80. This will be accomplished by having pump 130 provide high pressurefluid to lower working chamber 80 through hydraulic switch valve 132.When the fluid pressure in lower working chamber 80 rises above thestatic pressure in fluid chamber 64 of hydraulic adjustable spring seatassembly 56, a control valve 140 can be opened to allow fluid flow toenter fluid chamber 64 of hydraulic adjustable spring seat assembly 56.The fluid pressure in fluid chamber 64 will push outer housing assembly62 upwards to raise vehicle body 16 and gradually take over the staticload for vehicle body 16 from hydraulic actuator assembly 90. Arestriction 142 limits the amount of fluid flow that leaves hydraulicactuator assembly 90 preserving pressure levels in hydraulic actuatorassembly 90.

For the final adjustment, the fluid pressure in both upper workingchamber 78 and lower working chamber 80 will be increased to maintainenough pressure to move hydraulic adjustable spring seat assembly 56 toits new position. When this final position of hydraulic adjustablespring seat assembly 56 is reached, control valve 140 will be closed.

When the static (or quasi-static) push-out force in lower workingchamber 80 must be lowered, first the fluid pressure in upper workingchamber 78 will be increased by providing pressurized fluid from pump130 through hydraulic switch valve 132. This will provide acounter-acting force. The pressure in lower working chamber 80 will below, near the pressure in low pressure accumulator 110. Control valve140 can be opened and fluid will flow from fluid chamber 64 of hydraulicadjustable spring seat assembly 56 into the low pressure side ofhydraulic actuator assembly 90. Restriction 142 will limit this flow toa level that is not distortive to the function of hydraulic actuatorassembly 90. Gradually the counter-acting rebound force generated byhydraulic actuator assembly 90 will be reduced. Control valve 140 ispreferably a low-flow bi-directional normally-closed hydraulic valve.

The present disclosure is not limited to hydraulic adjustable lowerspring seat assembly 56. FIG. 4 illustrates a strut assembly 236. Strutassembly 236 comprises shock absorber 30, coil spring 32, top mountassembly 38, a part of the sprung portion of the vehicle, and knuckle 40which is a portion of the unsprung portion of the vehicle. The abovediscussion regarding strut assembly 36 in relation to top mount assembly38 applies to strut assembly 236 also. The difference between strutassembly 236 and strut assembly 36 is that upper spring seat 46 has beenreplaced with upper spring seat assembly 246 and lower spring seatassembly 56 has been replaced with lower spring seat 256.

Upper spring seat assembly 246 is a hydraulically adjustable spring seatassembly which is attached to top mount assembly 38. Coil spring 32 isdisposed between upper spring seat assembly 246 and lower spring seat256. Hydraulic adjustable spring seat assembly 246 includes an innerhousing assembly 260 attached to top mount assembly 38 and an outerhousing assembly 262 that is attached to both inner housing assembly 260and coil spring 32. Inner housing assembly 260 and outer housingassembly 262 define fluid chamber 64. When fluid is added to fluidchamber 64, outer housing assembly 262 will move downward along innerhousing assembly 260, as illustrated in FIG. 4. This movement will raisevehicle body 16 with respect to front suspension 14. When fluid isremoved from fluid chamber 64, outer housing assembly 262 will moveupward along inner housing assembly 260, as illustrated in FIG. 4. Thismovement will lower vehicle body 16 with respect to front suspension 14.Fluid chamber 64 is in fluid communication with shock absorber 30 asdescribed above.

The operation and function of hydraulically adjustable spring seatassembly 246 in conjunction with hydraulic actuator assembly 90 is thesame as discussed above for adjustable spring seat assembly 56. FIG. 4represents the adjusting of the upper spring seat rather than the lowerspring seat illustrated in FIG. 2.

The advantages of the systems described above include a low costaddition of static load leveling and height adjustment capability to theactive suspension system and the ability to lower energy consumption andincrease roll control performance in long corners of hydraulic actuatorassembly 90.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A corner assembly comprising: a top mountassembly; a wheel assembly; a shock absorber disposed between said topmount assembly and said wheel assembly, said shock absorber including apressure tube defining a first fluid chamber and a piston slidablydisposed within said pressure tube, said piston dividing said firstfluid chamber into an upper working chamber and a lower working chamber;an upper spring mount attached to said top mount assembly; a lowerspring mount attached to said wheel assembly; a spring disposed betweensaid upper spring mount and said lower spring mount; wherein one of saidupper spring mount and said lower spring mount is adjustable, said oneof said upper spring mount and said lower spring mount includes: aninner housing assembly attached to one of said wheel assembly and saidtop mount assembly; an outer housing assembly attached to said spring;and a second fluid chamber disposed between said inner housing assemblyand said outer housing assembly, said second fluid chamber being influid communication with said first fluid chamber defined by saidpressure tube of said shock absorber.
 2. The corner assembly accordingto claim 1, wherein said inner housing assembly is attached directly tosaid shock absorber.
 3. The corner assembly according to claim 1,wherein said second fluid chamber is in fluid communication with saidlower working chamber defined by said shock absorber.
 4. The cornerassembly according to claim 1, wherein said fluid chamber is a sealedfluid chamber.
 5. The corner assembly according to claim 1, wherein saidlower spring mount is adjustable: said inner housing assembly isattached to said wheel assembly; said outer housing assembly slidablyengages said inner housing assembly.
 6. The corner assembly according toclaim 5, wherein said inner housing assembly is attached directly tosaid shock absorber.
 7. The corner assembly according to claim 5,wherein said second fluid chamber is in fluid communication with saidlower working chamber defined by said shock absorber.
 8. The cornerassembly according to claim 5, wherein said fluid chamber is a sealedfluid chamber.
 9. The corner assembly according to claim 1, wherein saidupper spring mount is adjustable: said inner housing assembly isattached to said top mount assembly; said outer housing assemblyslidably engages said inner housing assembly.
 10. The corner assemblyaccording to claim 9, wherein said inner housing assembly is attacheddirectly to said shock absorber.
 11. The corner assembly according toclaim 9, wherein said second fluid chamber is in fluid communicationwith said lower working chamber defined by said shock absorber.
 12. Thecorner assembly according to claim 9, wherein said fluid chamber is asealed fluid chamber.
 13. The corner assembly according to claim 9,wherein said second fluid chamber is in fluid communication with saidupper working chamber defined by said shock absorber.
 14. The cornerassembly according to claim 1, wherein said second fluid chamber is influid communication with said upper working chamber defined by saidshock absorber.